In this R21 grant application, we propose here to study gene delivery to inhibit HIV replication and HIV toxicity for CNS cells. HIV encephalopathy is a common and potentially devastating complication of AIDS. Development of HW encephalopathy largely reflects HIV infection of brain cells, especially monocyte-derived macrophages (MDM) and microglia. It also may involve toxicity of certain HIV proteins for neurons. We will use gene delivery techniques to study inhibition of H1V infection and replication in primary cultured human MDM and microglia, and to examine protection of neurons from the ability of HIV gp120 envelope glycoprotein to induce apoptosis. Recombinant gene delivery vehicles derived from Talphag-deleted SV40 (rSV40s) permanently transduce unselected key CNS targets for HW, including microglia, neurons, and monocyte-derived macrophages (MDM) with >98% efficiency in vitro. We have found that HIV replicates in MDM and microglia, and that rSV40s carrying HIV inhibitory transgenes protect these cells from HIV replication. We have found as well that gp120 causes apoptosis in cultured neurons, and that rSV40 vectors that downregulate cell membrane CXCR4 or that provide antioxidant enzymes, such as catalase, protect these neurons. We propose to exploit these promising findings to study rSV40 gene delivery to protect the CNS cells from HIV. This proposal is based on the following hypothesis: To test this hypothesis, we propose the following specific aims: 1.) Identify optimal transgenes individually and in combination to inhibit HIV-1 in CNS cells. 2.) use gene delivery to protect NT2-derived neurons from apoptosis induced by HIV gene products. Despite the frequency and dire consequences of CNS HIV infection, people afflicted with HIV encephalopathy have few treatment options. We propose to address this therapeutic challenge using rSV40 gene delivery to the CNS, both to protect the brain from HIV infection and to mitigate HIV-induced CNS dysfunction.